


For Science

by PocketSizedWolf



Category: Sherlock (TV)
Genre: F/M, Light Bondage, M/M, Multi, Science, Service Submission, Sexual Experimentation
Language: English
Status: In-Progress
Published: 2014-11-03
Updated: 2015-01-01
Packaged: 2018-02-23 21:52:29
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 3,187
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/2557022
Author URL: https://archiveofourown.org/users/PocketSizedWolf/pseuds/PocketSizedWolf
Summary: <blockquote class="userstuff">
              <p>Sherlock asks John and Mary to help with an ongoing experiment.</p>
            </blockquote>





	1. Chapter 1

Mary closed the book she'd been reading and glanced up at Sherlock and John, who sat in their armchairs, lost in the thought of what they were doing. John, his laptop on his lap, was typing away furiously, no doubt typing up the happenings of their latest case. Sherlock, on the other hand, was reading papers that had been found at the scene of the crime. She wasn't sure what they contained, but he seemed utterly enthralled by them.

Mary rose from her seat and moved towards the kitchen  
"Anyone want a cuppa?" She asked softly, her fingers brushing through John's hair as she moved past him. He grabbed her wrist, pulling her back towards him and planting a soft kiss on the palm of her hand.  
"I'm fine"  
"Sherlock?"  
Sherlock's eyes snapped up and he shook his head. Mary tilted her head for a moment, confused by the look in his eyes before disappearing into the kitchen.

"What are you reading?" John asked as Mary clicked on the kettle in the kitchen.  
"Science documents." The detective paused. "John, what's sex like?"  
"What?"  
"What's sex like?"  
"Why are you asking me that?" John frowned, confused by his best friend's curiosity in things he'd never before taken an interest in.  
"I've spent years avoiding anything to do with it.. I'm curious."  
"You're curious about sex?"  
"I'm curious about everything to do with it."  
John paused, frowning, clueless as to what to say, and not expecting the next words that came out of Sherlock's mouth.  
"Can I have sex with Mary?"  
"What?"  
"For science, John."  
"Sherlock, you're not having sex with my wife. For science or not. Why can't you have sex with another woman?"  
"I don't find other women attractive." Sherlock shrugged "Mary is.." he stopped himself, shrugging "she's the only woman I've found.."  
"What?"  
"Arousing"  
"God Sherlock.." John slammed his laptop closed and placed it on the table beside him, closing his eyes. He couldn't deny that the idea of his wife and Sherlock wasn't slightly erotic. The thought of Sherlock's dark curls between his wife's parted thighs, Mary's moans of pleasure filling the room.. He would quite like to watch that. "What if she doesn't agree?"  
John asked after a few moments of silence. He could hear Mary stirring her tea in the kitchen.  
"Is that a yes?"  
"It's up to Mary.."  
"What's up to Mary?" Mary's voice reached his ears and he reached for her hand, pulling her onto his lap.  
"Sherlock wants to have sex with you"  
"For science" Sherlock chimed in.  
"What? Why me?"  
"Oh we've just been through this. You're the only woman he finds arousing."  
"And.. How do you feel about this?" Mary asked softly.  
"I said its up to you. But I'd only be comfortable with it if I could watch"  
"Right." Mary paused, looking at Sherlock's face. She could feel John growing hard beneath her arse and realised that he might be a little more alright with the idea than he was letting on. "Just the once?"  
"Well.. There were a few things I wanted to.. Test.. With your consent"  
"So it's an ongoing experiment then?"  
"Yes" Sherlock shrugged  
"Alright. But only when John is there.. And only for as long as he's comfortable with.. Alright?"  
"Yes"

Mary lay on Sherlock's bed, staring up at the ceiling. She wasn't exactly sure how they had ended up here, but decided it was better to just go with it. She turned her head to the left, looking at John sat in the corner. Gently, he moved towards her, kissing her on the lips before moving back to his seat. The sound of Sherlock clearing his throat in the doorway caused her to turn her head in time to watch the consulting detective shrugging his purple shirt from his shoulders and closing the door behind him.

He moved to the bed and placed his knees either side of Mary's waist, attempting to remember everything he'd read and also focus on what he was actually doing. His fingers moved to her shirt, slowly unbuttoning the white material, revealing the plain white bra she'd worn to work. Mary shifted herself, peeling her shirt off completely and tossing it to the floor.  
"You look nervous"  
"I'm fine.." Sherlock forced a smile, and Mary tilted her head.  
"Am I allowed to help, or does this void the experiment?"  
"You can help.."  
Mary smiled, pressing the palm of her hand to his cheek before pressing her lips to his. It took a moment before Sherlock began to kiss back, but when he did, it was timid and so very un-Sherlock that Mary mentally chuckled to herself. In the corner of the room, John shifted himself, only too aware of the growing bulge in his trousers. He wasn't sure this was normal, being so turned on by the image of his wife and his best friend, but they were both ridiculously beautiful.

Sherlock's fingers unhooked her bra, and he pulled it from her shoulders, removing his lips from hers and kissing slowly down her neck and over her chest. Mary lay back, allowing him to continue with his 'experiment' as his lips trailed further and he kissed over each of her breasts, momentarily sucking each of her nipples in turn and causing a gasp of air to escape from Mary's lips.

The reaction amused Sherlock, and he continued to suckle on her right nipple as his fingers pinched and pulled the left. Gently, he tugged the pink nub between his teeth, amused by Mary's hissing, a mixture of pleasure and pain. John watched, already uncomfortable, but more due to how tight his trousers had become, more than the sight before him. Satisfied with his experiment so far, Sherlock's mouth switched sides, toying with the line between pleasure and pain for Mary as his fingers moved to unbutton her trousers and slip them off.

Sherlock pulled back from Mary to look at the sight of her before him, dressed in nothing but a thin pair of bikini briefs. She was delightful, and he could feel himself growing hard in his trousers. There would be time for that later, though, he reminded himself as he slid her panties down her legs and tossed them in John's direction.

Gently, Sherlock ran his fingers along the smooth lips of Mary's pussy, biting down on his lower lip. He wanted to taste her, but he wanted to see how she reacted to his touches first. Careful to avoid touching her clit, Sherlock brushed his fingers over her flesh, before slowly sinking two fingers into her wet hole, pushing them up to the knuckle before slowly fucking her with them. Mary's breathing became more shallow, her body clenching around his fingers. Sherlock smirked, moving his thumb to tenderly caress her clit, glancing at John as Mary moaned in pleasure, her body squirming slightly at every movement of the inexperienced Consulting Detective.

Unable to wait much longer, Sherlock pulled his fingers from Mary's hot pussy and lowered his head, hooking Mary's legs over each of his shoulders before finally allowing himself to taste Mrs Watson's juices. She tasted divine, just as he'd dreamed she would on those nights where, unable to chase thoughts of her from his mind, he'd reluctantly wanked himself off to mental images of how he thought her body would look naked and twitching in pleasure caused by his tongue. Later, he may admit that he'd slightly manipulated his best friend into letting him fuck his wife, but one glance to John in his current position told him that John was enjoying it as much as he was.

As Mary came from Sherlock's attention, he pulled back and licked his lips.  
"You taste just as good as I thought you would.. Are you alright to carry on, or do you need to rest?"  
"I'm fine.." Mary panted softly as she watched Sherlock slipping out of his trousers and boxers, revealing his 8 inch cock, hard and ready for the next part of Sherlock's experiment.  
"At some point in the future.." Sherlock smirked, noticing Mary's eyes on his cock, "I may ask you to perform oral sex on me, but from what I've read, asking now may prevent the next part of my experiment taking part so I shall refrain for now.."

Without another word, Sherlock pressed his lips to Mary's, kissing her deeply as his hands spread her thighs once more. Pulling back from the kiss for a moment, he asked  
"Are you ready?"  
"God yes.." Mary panted softly, before letting out a moan of ecstasy as Sherlock's cock pushed slowly into her.

If she didn't know any better, she would have been sure that Sherlock had done this before. His cock pushing in and out of her was ridiculously pleasurable, and he altered his speed so she could never tell how hard each of his thrusts we're going to be. Sherlock pulled her into another kiss as he continued to thrust into her, his eyes looking to John in the corner, whose trousers had joined the pile of clothes on the floor and he was sure his boxers soon would too.

Mary's nails dug into his back as she came around his cock. The sensation was something he wasn't expecting. It was as though her cunt was milking him, begging him for every drop of his seed and his cock was only too happy to comply as he erupted inside her. Sherlock pulled out and sat back at the end of the bed, watching Mary's chest rise and fall as she struggled to catch her breath. The sight of her was erotic, and would keep him company through every lonely night he spent for the next year, he was sure. He glanced to John, who's hand was moving slowly in his boxers, and shook his head.  
"Your turn now, John. Fuck your wife. Describe how it feels to me."

John didn't need to be asked twice and, after confirming that it was alright with Mary, ('Fuck yes' had been her response), John entered his wife, feeling her already sopping wet with a combination of Sherlock's sperm and her own juices.

"How does it feel?" Sherlock asked again after John has thrust a few times.  
"Warm.. Silky.." John panted "and I'm very aware of your cum inside her.. It feels good though.. She always feels good.." He panted as his finger moved to tickle Mary's clit. Mary gasped in a combination of ecstasy and agony, her body tender from the orgasms before the one that was building. Both of the Watsons knew they wouldn't last much longer, and as John pressed the most passionate kiss he'd ever given her to her lips, they came together.

As they lay together on Sherlock's bed, John still buried inside Mary, his arms holding her to his chest, kisses planted along her hairline, Sherlock pulled his dressing gown on.  
"Same time tomorrow for my second experiment?"


	2. Chapter 2

"And what does John have to say?" Sherlock asked Mary as she returned to the room, slipping her phone back into her pocket.  
"He said we can get started without him. He's been pulled in to help with a late night clinic but he doesn't want to delay your experiments."  
"That's very.. Considerate of him"  
"Isn't it?" Mary smirked slightly, moving to sit in John's arm chair.   
Sherlock studied her for a moment as he thought about the previous evening, her naked body twitching in pleasure beneath him. He closed his eyes, allowing the images to flood his senses, reminding him how she'd felt around him. Mary watch him curiously, her eyes focussed on his face, watching as a particular muscle in his brow twitched.

When he opened his eyes, Mary was no longer sat in John's armchair, causing Sherlock to frown slightly until his eyes found her, kneeling by his legs.  
"You said yesterday that you wanted to experience oral sex?" she said softly, a light tone of seduction in her voice. Sherlock swallowed. He'd not been expecting that. He stared at her lips for a few moments, before nodding slightly, not fully committing to an answer.  
"Well.. We could always.. Experiment with that for now, until John comes?" she suggested, sitting back on her heels and looking the Consulting Detective in the eye, waiting for him to decide.

It didn't take Sherlock long to come to a decision. Gently, he unbuckled his belt, dropping it to the floor beside his chair, and unbuttoned his trousers. Mary shifted forward, helping him to tug them off, along with his boxers. Sherlock was already hard by the time he was naked from the waist down, and Mary swallowed slightly as she saw the true size of the cock that had made love so sweetly to her the night before. She licked her lips softly, before moving herself between his thighs, allowing her warm breath to wash over his flesh.

Sherlock watched her, his fingers immediately pushing into Mary's hair, pulling the loose strands from her face, wanting to get a better look of her face as her tongue touched his shaft. As her eyes met his, the head of his cock disappeared into her warm mouth, her tongue drawing delicate patterns on his flesh that caused him to hiss softly. His eyes snapped closed as he focussed on the sensation of Mrs Watson's mouth. She began to move her lips slowly up and down his cock, her saliva causing the air to feel cold when he wasn't within her mouth. It didn't take long for the familiar twitch of the approaching orgasm to cause his hips to buck slightly. Mary gripped him by the waist, taking a little more of him into her mouth as her tongue brushed against the underside of his cock. His fingers tightened in her hair as the wave of orgasm washed over him and he felt himself release in her mouth. He looked down at Mary as he pulled out of her mouth, slightly breathless. She gave him a soft smile, before opening her mouth, showing him the lump of his cum that sat on her tongue. She barely had chance to swallow it before he moved to her, catching her lips with his and kissing her deeply.

He wasn't sure how he had gotten to the point in his life where he had spent an hour of his time lying on top of his best friend's wife on the floor of 221b Baker Street kissing her, but he was sort of glad he had. It had gotten to the point where this wasn't so much about the experiment any more, but rather, he was in love with Mary Watson, and was using his naivety in the intimacy department as a means of getting what he wanted. He was aware just how manipulative that made him, but Mary seemed to be doing very little protesting. He took a moment to register everything about the way their bodies were laying, the way one of her legs was slightly wrapped around his bare leg, the way her flesh felt beneath the hand resting on her hip as her shirt rode up, the way her lips felt soft against his, and the way she tasted. He pulled back gently, breaking their kiss, and lightly pushed the hair from her face.

"What is it?" she asked after a few moments of him staring at her "is there something wrong?"  
"No.. You're just.. beautiful" he could swear his heart was about to burst when she smiled at that, watching as it lit up her face. Everything about her was beautiful, and he wasn't sure how long he was going to be able to continue with this game before his true feelings spilled out. He couldn't resist kissing her again, a little more forcefully this time. His fingers moved to unbutton her shirt, pushing it from her shoulders and letting her pull it off. He gently cupped her breasts, massaging them lightly, his thumbs running over the pretty lace pattern that decorated the top of the cups. She moaned softly into the kiss when his thumbs moved to seek out her nipple through the material, her hips lifting slightly, momentarily grinding against his, causing Sherlock to harden once more.  
"How long until John gets here?" he asked, resting his forehead against hers.  
"Another hour or so, maybe.."  
"Oh"  
"Yeah.. It does seem a shame to waste that.." she smiled again, nuzzling his cheek slightly before he felt her hot breath against his ear, "so let's not.."

He didn't need asking twice. Mary's clothes didn't remain on her body for much longer, and as he was pulling off her thin lace panties, Sherlock pondered a way to make this different to the last time, continuing his 'experiment' disguise.

She looked just as delicious from behind, Sherlock found as he bent her over his desk. Mary's fingers pressed against the wood as Sherlock's arm wrapped around her waist, seeking out her heat before gently stroking her clit. He pressed a gentle kiss to her neck as his free hand guided himself into her warmth. Mary let out a soft gasp as Sherlock pushed into her, his hands moving to grip her waist as he slowly began to fuck her. There was something about him, his size perhaps, or just his general technique, that Mary found addictive. He brushed against her G-Spot, causing a soft "oh" to escape her lips, her nails scratching on the wood of the desk.

Sherlock's thrusting increased in force as his hands moved to toy with her breasts, tugging and pinching her nipples in a delightful mess of sensation. He bit down gently on her neck as he began to enter her with a force only John would be able to match, one that knocked the air from her lungs and almost made her cum immediately. Mary closed her eyes as the ecstasy filled her body, allowing herself to ride the wave of her orgasm as it suffocated her, causing her to moan so loudly that she was sure that Mrs Hudson had heard from downstairs. Sherlock didn't stop. His hands gripped her breasts for a moment as he pulled her body back against his, his cock still moving forcefully within her. Her body clenched and unclenched around him, begging him for his seed, desperately wanting to feel him release with her. Sherlock had other ideas, however, and one of his hands moved down her body, seeking out her clit, and gently stroking her until her second orgasm washed over her. Only then did he allow himself to release within her.

Panting softly, Sherlock sat back in his chair, watching Mary as she attempted to catch her breath. She could barely feel her legs as she turned to slump back down in John's armchair.  
"Wow.. For someone who's only been doing this for two days.. Wow.. Please tell me you've not finished with these experiments yet.."  
"Oh no" Sherlock smirked warmly as he looked over her, subconsciously licking his lips "I still have a few things I'd like to try"


End file.
